In the manufacture of semiconductor devices, ion implantation systems are employed to dope a semiconductor wafer or other workpiece with impurities. In such systems, an ion source ionizes a desired dopant element, which is extracted from the source in the form of an ion beam. The ion beam is typically mass analyzed to select ions of a desired charge-to-mass ratio and then directed at the surface of a semiconductor wafer in order to implant the wafer with the dopant element. The ions of the beam penetrate the surface of the wafer to form a region of desired conductivity, such as in the fabrication of transistor devices in the wafer. A typical ion implanter includes an ion source for generating the ion beam, a beamline assembly including a mass analysis apparatus for mass resolving the ion beam using magnetic fields, and a target chamber containing the semiconductor wafer or workpiece to be implanted by the ion beam.
Typically, the ions generated from the ion source are formed into a beam and directed along a predetermined beam path to an implantation station. The ion beam implanter may further include beam forming and shaping structures extending between the ion source and the implantation station. The beam forming and shaping structures maintain the ion beam and bound an elongated interior cavity or passageway through which the beam passes en route to the implantation station. When operating the ion implanter, this passageway is typically evacuated to reduce the probability of ions being deflected from the predetermined beam path as a result of collisions with air molecules.
The mass of an ion relative to the charge thereon (i.e., charge-to-mass ratio) affects the degree to which it is accelerated both axially and transversely by an electrostatic or magnetic field. Therefore, the beam that reaches a desired area of a semiconductor wafer or other target can be made very pure since ions of undesirable molecular weight will be deflected to positions away from the beam and implantation of other than desired materials can be avoided. The process of selectively separating ions of desired and undesired charge-to-mass ratios is known as mass analysis. Mass analyzers typically employ a mass analysis magnet creating a dipole magnetic field to deflect various ions in an ion beam via magnetic deflection in an arcuate passageway that will effectively separate ions of different charge-to-mass ratios.
The ion beam is focused and directed at a desired surface region of the workpiece in the target station, wherein the energetic ions of the ion beam are accelerated to a predetermined energy level to penetrate into the bulk of the workpiece. The ions, for example, are embedded into the crystalline lattice of the material to form a region of desired conductivity, with the energy of the ion beam generally determining the depth of implantation. The ion beam may be a spot beam (e.g., a pencil beam), wherein the workpiece is mechanically scanned in two dimensions orthogonal to the generally stationary spot beam; a ribbon beam, wherein the beam is electromagnetically scanned in one direction across the workpiece while the workpiece is mechanically scanned in an orthogonal direction; or an electromagnetically scanned beam that is electromagnetically scanned in two directions across a stationary workpiece. Examples of ion implantation systems include those available from Axcelis Technologies of Beverly, Mass.
Conventionally, a typical ion implantation system comprises a processing chamber, wherein the workpiece resides on a workpiece holder within the processing chamber during implantation. The processing chamber maintains a processing environment that is typically separate from other environments, wherein cross-contamination from the processing environment to the other environments is generally limited. In an ion implantation system employing a mechanical scanning of the workpiece, the workpiece holder is typically coupled to a scanning device within the processing chamber, wherein the scanning device is operable to move the workpiece holder in one or more directions with respect to the ion beam. Further, a beam monitoring device (such as a Faraday cup) is typically aligned with the ion beam within the process chamber for process feedback.
In some processing schemes, cluster tools are utilized to perform several different processes on a single workpiece, wherein the workpiece is transported between various processing environments within the cluster tool. For example, FIG. 1 illustrates a conventional cluster tool 10, wherein the cluster tool is configured to perform a variety of processes on a workpiece 15. The cluster tool 10, for example, comprises a first ion implanter 20, a second ion implanter 25 an etch station 30, a resist asher 35, and a load lock chamber 40 surrounding a central workpiece transfer station 45. Each of the first ion implanter 20, second ion implanter 25, etch station 30, and resist asher 35 comprises its own respective independent processing chamber 50A-50D that is selectively isolated from the workpiece transfer station 45 by respective gate valves 55A-55D, wherein each processing chamber has an independent processing environment 60A-60D for processing the workpiece 15. Further, each processing chamber 50A-50D comprises its own workpiece holder 65A-65D, wherein, in the case of the first and second ion implanters 20 and 25, the workpiece holders 65A and 65B are further coupled to a respective first and second scanning device 70A and 70B. Still further, in the case of the first and second ion implanters 20 and 25, a respective first and second beam monitoring device 75A and 75B are positioned within the respective processing chambers 50A and 50B for monitoring respective first and second ion beamlines 80A and 80B associated with the respective implanter.
In operation, the workpiece 15 is conventionally transferred between the plurality of processing chambers 50A-50D by a workpiece handler 80, based on the desired processing of the workpiece. For example, when differing ion species are desired to be implanted into the workpiece 15, the first and second ion beamlines 85A and 85B of the respective first and second ion implanters 20 and 25 are configured to have differing ion species associated therewith. Accordingly, the workpiece 15 is transferred from the load lock chamber 40 through the gate valve 55A to the first processing chamber 50A and placed on the workpiece holder 65A coupled to the first scanning device 70A within the processing chamber 50A. The gate valve 55A is then closed, the first processing chamber 50A is evacuated, and the workpiece 15 is scanned through the first beamline 85A via the first scanning device 70A, wherein the first beamline is monitored by the first beam monitoring device 75A within the processing chamber 50A.
Once the desired implant by the first implanter 20 is complete, the gate valve 55A is opened, and the workpiece 15 is transferred out of the processing chamber 50A of the first implanter and back into the transfer station 45. The workpiece is 15 is then transferred through the gate valve 55B into the processing chamber 50B of the second implanter 25 and placed on the workpiece holder 65B coupled to the second scanning device 70B within the processing chamber 50B of the second implanter. The gate valve 55B is then closed, and the processing chamber 50B is evacuated. The workpiece 15 is then scanned through the second beamline 85B of the second implanter 25 via the second scanning device 70B, wherein the second beamline is monitored by the second beam monitoring device 75B within the processing chamber 50B. When the desired implant by the second implanter 25 is complete, the gate valve 55B is opened, and the workpiece 15 is transferred out of the processing chamber 50B of the second implanter and back into the transfer station 45, wherein further processing may or may not be performed.
The conventional cluster tool described above, however, is costly, since each ion implantation system 20 and 25 has its own respective dedicated process chamber 50A and 50B, scanning device 70A and 70B, beam monitoring device 75A and 75B, and typically, its own controller (not shown) for controlling each implantation system. Therefore, it is desirable to provide an improved ion implantation system cluster tool, wherein efficiencies can be increased by sharing common components between multiple ion beamlines, thus decreasing ownership costs associated with having multiple beamlines.